In planar junction semiconductor devices, junction curvature and device geometry curvature result in an increased electric field strength at the edge of the semiconductor device. This increased electric field causes premature device breakdown.
Several different types of edge termination structures have been employed in the past in an attempt to redistribute or reduce the electric field strength at the edge region of planar devices and increase the breakdown voltage. Edge termination structures have included guard rings and field plates, among others. However, these structures either require a large silicon area, require additional manufacturing process steps, or are unsuccessful in reaching near-ideal breakdown characteristics.
Accordingly, it is highly desirable to have an edge termination structure that is capable of increasing the breakdown voltage and eliminating the problems encountered in conventional edge termination schemes.